July 2019
Volume 60, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2019
Evaluation of a Simplified non-invasive Method for Obtaining Samples from Corneal Ulcers in suspected Microbial Keratitis.
Author Affiliations & Notes
  • Tobi Frances Somerville
    Department of Eye and Vision Sciences, University of Liverpool, Liverpool, United Kingdom
    St Pauls Eye Unit, Royal Liverpool University Hospital, Liverpool, United Kingdom
  • Timothy Neal
    Department of Infection and Immunity, Royal Liverpool University Hospital, Liverpool, United Kingdom
  • Caroline Corless
    Department of Medical Microbiology, Royal Liverpool University Hospital, Liverpool, United Kingdom
  • Mal Horsburgh
    Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
  • Stephen Kaye
    St Pauls Eye Unit, Royal Liverpool University Hospital, Liverpool, United Kingdom
    Department of Eye and Vision Sciences, University of Liverpool, Liverpool, United Kingdom
  • Footnotes
    Commercial Relationships   Tobi Somerville, None; Timothy Neal, None; Caroline Corless, None; Mal Horsburgh, None; Stephen Kaye, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 4692. doi:
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      Tobi Frances Somerville, Timothy Neal, Caroline Corless, Mal Horsburgh, Stephen Kaye; Evaluation of a Simplified non-invasive Method for Obtaining Samples from Corneal Ulcers in suspected Microbial Keratitis.. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4692.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : To evaluate microbial isolation rates following the introduction of a simplified non-invasive method for collecting samples from cases of clinically suspected microbial keratitis over a 2 year period.

Methods : Data was retrospectively collected by the department of medical microbiology at the Royal Liverpool University Hospital for all patients that had corneal samples taken for suspected microbial keratitis for the period April 2016-April 2018. Samples were collected from ulcers prior to April 2017 by scraping the base of the ulcer with a surgical blade (corneal scrape). From April 2017, samples were collected by placing a 12-mm-diameter polytetrafluoroethylene (PTFE) corneal impression membrane (CIM) over the ulcer. The blade and CIM were transported in brain heart infusion before being plated and sub-cultured in an enrichment medium.

Results : A total of 1053 cases were included, comprising samples obtained from 448 (42.5%) cases using a corneal scrape and 605 (57.5%) using a CIM. Microorganisms were isolated from 90 (20.1%) cases using a corneal scrape and 396 (65.5%) using a CIM (p<0.001). More than one isolate was identified in 9 (10.0%) and 76 (19.2%) of samples using a corneal scrape and CIM respectively. There was a significant increase in the isolation of pathogens in the CIM group compared to the corneal scrape group (p<0.001); including Staphylococcus aureus (2.0% to 10.1%), Streptococcus pneumoniae (1.3% to 1.7%), Streptococcus pyogenes (0 to 0.3%), Serratia spp. (0.9% to 2.2%), Enterobacteriaceae spp. (0.5% to 1.5%), Moraxella spp. (0.7% to 1.2%) and Pseudomonas spp. (2.0% to 2.6%). Fungi were isolated in 1.1% of the corneal scrape group and 0.5% of the CIM group (p=0.252). There was a significant increase in the isolation of Staphylococcal epidermidis (3.3% to 27.8%) using a CIM (p<0.001).

Conclusions : The difficulties in isolating the causative microorganism has led to increased empirical treatment of microbial keratitis. The introduction of the simplified CIM sampling method led to a significant increase in the isolation of pathogens from cases of suspected microbial keratitis but also an increase in Staphylococcal epidermidis.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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